In this study, water allocation managements between irrigation and rainfed lands were surveyed in different climate conditions. The optimization model results in the Qazvin Plain indicated net benefit increased under new management in case of water conveyance from 2000, 4000, 6000, 8000 and 10000 meters in a climatically normal year to be 11.1, 13.5, 19.2, 16.6 and 15.8 percent, respectively, while in a wet year 9.0, 10.9, 17.0, 15.9 and 13.4 and in a dry year 8.05, 12.5, 16.1, 19.1 and 19.9, respectively. Barley was the best choice for deficit irrigation in three climate conditions. Depths of deficit irrigation were 20, 25 and 30 mm in the first decade of November and 50, 50 and 60 mm in the second decade of May in normal, wet and dry conditions. Also lentil was the first choice for supplementary irrigation. The best treatments for supplementary irrigation in lentil rainfed fields were 75 mm in the third decade of May in normal years, 75 mm in the second decade of May in wet years and 100 in the second decade of May in dry years.